Indrek Kelder, a 27-year-old accountant, thought he was being recruited for tests of "some kind of vitamin." It seemed like a great deal: Free air tickets to Switzerland, two weeks at a comfortable clinic and a cash stipend of several hundred dollars, more than a typical monthly salary in this struggling Baltic nation.

In October 1998 he jetted to Basel, a pristine mountain town of flower boxes and church spires, expecting a transfer to a three-star hotel. Instead he found himself in a sterile clinic filled with beds, where he would be tested for a drug whose risks and purposes he did not understand. He said he wanted to back out, then realized it was dark, the airport was an hour away and he had no obvious alternative.

Eventually he signed a consent form written in German, a language he could not read. When he finally got an English translation, he said, the clinic doctor agreed only to show him a copy. Kelder said he had no idea what tablets he swallowed during the next two weeks. "Maybe it was written between all this mumbo jumbo."

His countryman Irme Petrimae arrived in Basel in January 1999 knowing almost nothing about the drug he was to take, and left after three weeks just as ignorant. "They told me something about skin disease," said the 22-year-old. "All these forms, and we didn't get any copies. I didn't like it, but when we were already there, it was too late to change our minds."

The clinic at which Kelder and Petrimae stayed ultimately shut down after authorities discovered that its operator, Van Tx Research Ltd., had filled many of its beds with people who didn't know they were in experiments, refugees seeking political asylum in Switzerland and drug addicts. It had performed 161 drug trials for some of the world's best-known pharmaceutical companies. A Swiss prosecutor is investigating fraud charges.

The case was "the most unpleasant experience ever in the short history of clinical trials in Estonia," said Alar Irs, an Estonian medical regulator.

The violations uncovered in the Van Tx case point to wider failures with patient consent procedures that some doctors and researchers say will increasingly occur as drug companies stage human tests in far-flung countries using naive, impoverished or uneducated patients.

Participants in human drug experiments are supposed to be fully informed of the risks they face during a test. The principle of "informed consent" lies at the heart of human drug testing contained in guidelines widely endorsed around the world. These rules ban coercion and trickery and give patients the right to withdraw from a test at any time for any reason. [See graphic]

But researchers and doctors say these principles have been breaking down as drug companies enroll thousands of test subjects at a time in Eastern Europe, the former Soviet Union, Africa, China, Latin America and elsewhere.

In some cases, unscrupulous operators just ignore the rules. In other instances the problems are more complex, involving such questions as whether an illiterate Third World villager who knows little about modern medicine can give informed consent in a way comparable to a Western patient.

Visits by Washington Post reporters to foreign test sites, as well as inspections and surveys of drug experiments overseas by various regulators and medical researchers, provided indications of widespread lapses.